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In an interview on "Fox & Friends" on Feb. 9, Conway encouraged viewers to "go buy Ivanka's stuff." A day earlier, President Trump had attacked Nordstrom department stores for dropping his daughter's line of clothes and accessories.

The ethics office recommended discipline because federal rules prohibit executive branch employees from endorsing products. The White House concluded that she was speaking "in a light, off-hand manner while attempting to stand up for a person she believed had been unfairly treated."

"Not taking disciplinary action against a senior official under such circumstances risks undermining the ethics program," Shaub wrote to a White House lawyer.

He said he is also concerned about the White House's "extraordinary" assertion that some OGE regulations don't apply to the president's staff.

"It is critical to the public's faith in the integrity of government that White House employees be held to the same standard of ethical accountability as other executive branch employees," he wrote.

The White House did not immediately respond to a request for comment from CNNMoney about the latest letter from OGE.